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Na, Mg and Al abundances as a population discriminant for nearby metal-poor stars
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2006 (English)In: Astronomy & Astrophysics, no 451, 1065-1079 p.Article in journal (Other (popular scientific, debate etc.)) Published
Abstract [en]

Aims. Parameters for 55 nearby metal-poor stars are determined using high-resolution spectroscopy. Together with similar data taken

from a recent analysis, they are used to show trends of their Galactic evolution with stellar [Fe/H] or [Mg/H] abundances. The

separation of abundance ratios between disk and halo stars is used as a basic criterion for population membership.

Methods. After careful selection of a clean subsample free of suspected or known binaries and peculiar stars, abundances of Mg, Na and Al are based on NLTE kinetic equilibrium calculations applied to spectrum synthesis methods.

Results. The relation between [Na/Mg] and [Fe/H] is a continuous enrichment through all three Galactic populations spanning a range

of values between a metal-poor plateau at [Na/Mg] = −0.7 and solar values. [Al/Mg] displays a step-like difference between stars

of the Galactic halo with [Al/Mg] ∼ −0.45 and the two disk populations with [Al/Mg] ∼ +0.10. [Al/Mg] ratios, together with the

[Mg/Fe] ratios, asymmetric drift velocities V, and stellar evolutionary ages, make possible the individual discrimination between stars of the thick disk and the halo. At present, this evidence is limited by the small number of stars, and by the theoretical and empirical uncertainties of stellar age determinations, but it achieves a high significance.

Conclusions. While the stellar sample is not complete with respect to space volume, the resulting abundances indicate the necessity

to revise current models of chemical evolution to allow for an adequate production of Al in early stellar generations.

Place, publisher, year, edition, pages
2006. no 451, 1065-1079 p.
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-25357DOI: doi:10.1051/0004-6361:20054434OAI: oai:DiVA.org:uu-25357DiVA: diva2:53131
Available from: 2007-02-12 Created: 2007-02-12 Last updated: 2011-01-11

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